The present invention relates generally to the field of telecommunications, and more specifically, to the field of cellular telephone user notification.
While the most common type of cellular telephone currently in use today is the analog cellular telephone, the use of digital cellular telephones is steadily increasing as development continues. It is generally understood that the term "digital cellular telephone" includes, at least, those cellular telephones which are capable of communicating through the code division multiple access (CDMA) method, the time division multiple access (TDMA) method, or the frequency division multiple access (FDMA) method, or any other multiple access method, either exclusively, in any combination, or in combination with an analog ability, in which case the telephones are also referred to as "dual mode" cellular telephones. Conventional cellular telephone communication systems, including both digital and analog systems, typically provide service by dividing an area into many smaller geographic areas, known as cells, each of which is serviced by a transmitter-receiver station, known as a cell site or base station. The cell sites are connected through land lines, or other communication links, to so-called mobile telephone switching offices (MTSO's) which are, in turn, connected to the public switched telephone network (PSTN).
As an analog cellular telephone begins to reach the boundary of a cell, it is common for the telephone to have difficulties in receiving a clear signal so that the user hears an increasing amount of ordinary static or noise from the analog receiver discriminator as the signal grows weaker. While the noise may be potentially annoying to a user, the noise nevertheless provides the user an opportunity to prepare for a potential disconnection by concluding the conversation or making provision for re-establishing the connection. While digital cellular telephones provide many advantages over analog cellular telephones, one known disadvantage is the abruptness of communication disconnections due to lack of noise or other warning. As a result, a user normally has no opportunity to prepare for a potential disconnection, and conversations can often be interrupted by sudden, unsuspected disconnections.
Also gaining popularity are various types of personal communication systems (PCS) and wireless private branch exchanges (PBX) which provide various other types of radio links into the PSTN. A privately owned PCS cell or wireless PBX typically provides service to specially equipped cellular telephones at little or no usage time cost while the telephones operate within its range, or microcell. However, when the cellular telephone travels outside the microcell, higher usage time rates are encountered since a public cellular provider begins supplying service to the telephone. Users are often unaware that such an inter-system handoff, as well as other types of changes in communication mode, are imminent, thus it would be desirable to provide a telephone which notifies users of imminent inter-system handoffs and other types of communication mode changes before the mode changes have occurred or preliminary system communication between cell sites begins.
There is, therefore, a need in the industry for a method and an apparatus which address these and other related, and unrelated, problems.